Import your footage into After Effects, you can drag and drop your footage into the timeline.

Once you've done that, you then create a "garbage" mask around the footage you want to keep in the footage using the pen tool. *This removes all unwanted area in your footage, *Check your footage to see if any of the footage you want ends up outside of your masked area with the timeline tool and if there is a problem adjust accordingly.

Next, when you are satisfied with the masked area, open keylight. Go to the top click Effects - Keying - Keylight(1.2).

Then select eyedropper in Screen Colour. *Pick the green closest to the edge of your subject.

Change the view in Keylight from "Final Result" to "Screen Matte". *White is what will be visible, and the black will be what is invisible.

Remove all gray from black and white areas.

Expand "Screen Matte" drop down menu.*Clip black and Clip white show up. You then make sure that gray that is around your subject gets darker and becomes reasonably darkened, but not so dark that it eats into your white area.After clipping the black, clip the white by sliding the value the opposite way until the white inside of your subjects grays and spots become whiter.*Make sure not to overdo either the clip black or clip white. Otherwise you will have problems with your footage.*

You may think that your subject looks to blocky or choppy in motion. If that happens, in keylight, change your Screen Pre-blur to about a value of 2 or desired.

Then change your "Screen Matte" view back to "Final Result".

If your subject happens to have some green around the edges, in keylight, you can Screen Shrink/Grow to remove it by using a desired negative value.

You may then close the keylight panel if you wish. *Always be sure to properly name your layers of the timeline.*